1. Field of the Invention
The present invention relates to an air pilot operated directional control valve which controls a fluid connection between a normally open valve port and selection valve ports by an air pilot pressure.
2. Description of the Related Art
A known two way-three port directional control valve which usually has one open inlet port and two outlet ports which can be selectively connected to the inlet port or two inlet ports and one open outlet port to which the inlet ports can be selectively connected is actuated by a spool or a diaphragm which is, however, rather complex in construction and expensive.
An air pilot operated directional control valve is also known, which is simple in construction and relatively inexpensive. However, there is no highly reliable pilot operated directional control valve hitherto known, due to, as example, possible cause of failure in the sliding parts being eliminated. In addition, in a known pilot operated directional control valve, it is very difficult to actuate a valve by a snap action which is desirable in order to control the fluid connection, when the pilot pressure exceeds a predetermined value.
The primary object of the present invention is, therefore, to provide an air pilot operated directional control valve in which the valve switches its flow paths in a snap action when the pilot pressure exceeds a predetermined value and in which no reverse switching of flow paths takes place by a slight fluctuation of the pilot pressure.